Bug 5003 - Remove all public-facing refs to hg.dreamwidth.org

http://bugs.dwscoalition.org/show_bug.cgi?id=5003

hg.dwscoalition.org has gone away, and we've moved on to GitHub, so this changes the few public references to hg.dws to point to github/dw instead.  

There's an accompanying pull request for the dw-nonfree repo.